"Mission complete", McGrath tweeted, showing Sully the dog.
With the passing of George H.W. Bush, it's a good opportunity to revisit the classic impression of the 41st president during a golden era on Saturday Night Live.
The casket carrying the remains of George H.W. Bush arriving at the U.S. Capitol where it will lie until Wednesday morning.
Sully will reportedly be traveling with the former President's casket on his flight to Washington, D.C. on Monday.
President Trump and first lady Melania Trump will attend the funeral service at the Washington National Cathedral, according to the White House.
The yellow Lab was trained by America's VetDogs, which places service dogs and guide dogs with veterans, active-duty service members and first responders. He frequently used a wheelchair toward the end of his life, and Sully provided assistance with daily life.
Though his time with Bush has ended, Sully will continue to serve by working with wounded USA veterans.
"Sully could open doors, pick up items and summon help", The Associated Press reported.
He will be joining the Walter Reed National Military Medical Center's Facility Dog Program after the holidays, America's VetDogs announced.
Bush will then be returned to Houston for burial Thursday at his presidential library at Texas A&M University.
The senior Bush and his wife, Barbara, a force in her own right, had four other children, sons Neil and Marvin, daughters Dorothy and Robin, who died in childhood.